Exodus 16:18, 33, 36

And when they measured it with an omer, he that gathered much had nothing over, and he that gathered little had no lack; they gathered every man according to his eating.

And Moses said unto Aaron, Take a pot, and put an omerful of manna therein, and lay it up before Jehovah, to be kept throughout your generations.

Now an omer is the tenth part of an ephah.